root.cpp

#include <iostream>
#include <iomanip>
#include <math.h>
using namespace std;
const double EPS = 1e-6;
inline double f(double x) { return x * x * x - 5 * x * x + 10 * x - 80; }

int main(void) {
    double root, x1 = 0, x2 = 100, y = 0.0;
    root = x1 + (x2 - x1) / 2;
    int triedTimes = 1;
    
    y = f(root);
    while (fabs(y) > EPS) {
        if (y > 0) 
            x2 = root;
        else 
            x1 = root;
        root = x1 + (x2 - x1) / 2;
        triedTimes++;
        y = f(root);
    }
    cout << setprecision(10) << root << endl;
    cout << triedTimes << endl;
    return 0;
}

get root of an equation using binary search.